Data communications networks have become ubiquitous. A typical data communication networks may include various computers, servers, nodes, routers, switches, hubs, proxies, and other devices coupled to and configured to pass data to one another. These devices are referred to herein as “network elements,” and may provide a variety of network resources on a network. Data is communicated through data communication networks by passing protocol data units (such as packets, cells, frames, or segments) between the network elements over communication links on the network. A particular protocol data unit may be handled by multiple network elements and cross multiple communication links as it travels between its source and its destination over the network. Hosts such as computers, telephones, cellular telephones, Personal Digital Assistants (PDAs), tablets and other types of consumer electronics connect to and transmit/receive data over the communication network and, hence, are users of the communication services offered by the communication network.
Network elements (e.g. Access Points (APs), mobility switches, edge switches, bridges and the like) are typically implemented to have a control plane that controls operation of the network element and a data plane that handles traffic flowing through the network. The data plane typically will have a collection of line cards having ports that connect to links on the network. Data is received at a particular port, switched within the data plane, and output at one or more other ports onto other links on the network. The packets are transferred across the network in accordance with a particular protocol, such as the Internet Protocol (IP).
One type of network is known as a Shortest Path Bridging (SPB) network. SPB technology provides logical Ethernet networks on native Ethernet infrastructures using a link state protocol to advertise both topology and logical network membership. Packets are encapsulated at the edge either in Media Access Control (MAC)-in-MAC 802.1ah or tagged 802.1Q/802.1ad frames and transported only to other members of the logical network. Unicast and multicast are supported and all routing is on symmetric shortest paths. Many equal cost shortest paths are supported.
Intermediate System To Intermediate System (ISIS) is a routing protocol designed to move information efficiently within a computer network, a group of physically connected computers or similar devices. ISIS accomplishes this by determining the best route for packets through a packet-switched network. The protocol was defined in ISO/IEC 10589:2002 as an international standard within the Open Systems Interconnection (OSI) reference design. Though originally an ISO standard, the IETF republished the protocol as an Internet Standard in RFC 1142. IS-IS has been called the de facto standard for large service provider network backbones.
SPB uses ISIS as the control protocol to transfer routing information between devices in an SPB Network acting as a transport network between access networks which may be running different protocols. In an SPB network, the ISIS Link State Database (LSDB) is used to advertise routing information. In addition to information about adjacencies with other SPB enabled devices the LSDB also includes reachability information for services outside the SPB network. Examples are—IPv4 unicast routes, IPv4 Multicast Routes, IPv6 unicast routes, IPv6 multicast routes, L2 virtual Service networks (VSNs), Unicast Backbone Media Access Control (BMAC) addresses etc.